TY - JOUR

T1 - Experimental strategies to measure the microbial uptake and mineralization kinetics of dissolved organic carbon in soil

AU - Li, Baozhen

AU - Hill, Paul W.

AU - Jones, Davey L.

AU - Zhu, Zhenke

AU - Zhran, Mostafa

AU - Wu, Jinshui

PY - 2020/5/30

Y1 - 2020/5/30

N2 - Soil organic matter turnover rates are typically estimated from mass loss of the material over time or from on rates of carbon dioxide production. In the study, we investigated a new way to characterize the concentration-dependent kinetics of amino acids used by measuring microbial uptake and mineralization of 14C-alanine. We measured the depletion from soil solution after additions 14C-alanine. The microbial uptake of 14C-alanine from soil solution was concentration-dependent and kinetic analysis indicated the operation of at least three distinct alanine transport systems of differing affinities. Most of the 14C-alanine depletion from the soil solution occurred rapidly within the first 10–30 min of the incubation after 10 µM to 1 mM substrate additions. At alanine concentrations less than 250 mM, the kinetic parameters for Km and Vmax of the higher-affinity transporter were 60.0 µM and 1.32 µmol g−1 DW soil h−1, respectively. The mineralization of alanine was determined and the half-time values for the rapid mineralization process were 45 min to 1.5 h after the addition at alanine concentrations below 1 mM. The time delay after its uptake into microbial biomass suggested that alanine uptake and subsequent respiration were uncoupled pattern. The microbial N uptake rate was calculated by microbial mineralization, and an estimated Km value of 1731.7±274.6 µM and Vmax value of 486.0±38.5 µmol kg−1 DW soil h−1. This study provides an alternative approach for measuring the rate of turnover of compounds that turnover very rapidly in soil.

AB - Soil organic matter turnover rates are typically estimated from mass loss of the material over time or from on rates of carbon dioxide production. In the study, we investigated a new way to characterize the concentration-dependent kinetics of amino acids used by measuring microbial uptake and mineralization of 14C-alanine. We measured the depletion from soil solution after additions 14C-alanine. The microbial uptake of 14C-alanine from soil solution was concentration-dependent and kinetic analysis indicated the operation of at least three distinct alanine transport systems of differing affinities. Most of the 14C-alanine depletion from the soil solution occurred rapidly within the first 10–30 min of the incubation after 10 µM to 1 mM substrate additions. At alanine concentrations less than 250 mM, the kinetic parameters for Km and Vmax of the higher-affinity transporter were 60.0 µM and 1.32 µmol g−1 DW soil h−1, respectively. The mineralization of alanine was determined and the half-time values for the rapid mineralization process were 45 min to 1.5 h after the addition at alanine concentrations below 1 mM. The time delay after its uptake into microbial biomass suggested that alanine uptake and subsequent respiration were uncoupled pattern. The microbial N uptake rate was calculated by microbial mineralization, and an estimated Km value of 1731.7±274.6 µM and Vmax value of 486.0±38.5 µmol kg−1 DW soil h−1. This study provides an alternative approach for measuring the rate of turnover of compounds that turnover very rapidly in soil.

KW - C-14 tracer

KW - Microbial uptake

KW - Carbon mineralization

KW - Turnover

U2 - 10.1007/s42832-020-0035-5

DO - 10.1007/s42832-020-0035-5

M3 - Article

VL - 2

SP - 180

EP - 187

JO - Soil Ecology Letters

JF - Soil Ecology Letters

SN - 2662-2289

IS - 3

ER -